Volcanoes General - 12 of 25
Volcanoes General FAQs - 25 Found
Scientists use the term magma for molten rock underground and lava for molten rock (and contained gases) that breaks through the Earth's surface. Originating many tens of miles beneath the ground, magma commonly contains some crystals, fragments of surrounding (unmelted) rocks, and dissolved gases, but it is primarily a liquid composed principally of oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese. Lava is red hot when it pours or blasts out of a vent but soon changes to dark red, gray, black, or some other color as it cools and solidifies. Very hot, gas-rich lava containing abundant iron and magnesium is fluid and flows like hot tar, whereas cooler, gas-poor lava high in silicon, sodium, and potassium flows sluggishly, like thick honey in some cases or in others like pasty, blocky masses.
Eruptions of Hawaiian Volcanoes: Past, Present, and Future, 2010, USGS General Interest Publication 117, 62 p.
Volcanoes, 1998, USGS General Interest Publication, 45 p.